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DTC codes / Chrysler codes / P1197

P1197 · ChryslerO2 Sensor 1/2 (Bank 1 Sensor 2) Slow During Catalyst Monitor

P1197 on Chrysler vehicles means the downstream oxygen sensor on bank 1 (sensor 2) is responding too slowly during the catalyst monitor test. The powertrain control module (PCM) ran its catalyst efficiency monitor and saw the rear sensor's voltage switching rate fall outside the expected window, so it flagged the sensor as lazy rather than reporting a converter efficiency fault.

SystemPowertrain
Code typeChrysler specific
SeverityLow
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Illumination of the check engine light, often with no other symptoms noticed by the driver
  • Slightly reduced fuel economy as the PCM loses confidence in rear-sensor feedback
  • Occasional rough idle or mild hesitation on some 2.4L and 3.3L Chrysler engines
  • A pending P1197 that reappears after a few drive cycles once the catalyst monitor runs
  • Failed state emissions inspection because the catalyst monitor will not complete
  • In rare cases, a faint sulfur or rich exhaust smell if the slow sensor masks a mixture issue

Common causes, most likely first

  1. Aged or contaminated downstream oxygen sensor that has drifted slow, especially past 100,000 miles
  2. Exhaust leaks ahead of the rear sensor, such as a cracked flex pipe or failed gasket, letting outside air pulse past the tip
  3. Wiring damage or corrosion at the rear sensor connector, including chafed harness near the floor pan
  4. A failing catalytic converter that is beginning to lose efficiency and is dragging the rear sensor signal with it
  5. An upstream oxygen sensor that is slow or biased, causing the PCM to misjudge the rear sensor's response
  6. Engine misfire or exhaust valve issues that introduce unburned fuel and skew the catalyst monitor
  7. PCM software calibration that is overly sensitive on certain Chrysler 2.4L and 3.3L applications

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data to confirm P1197 is active and not a stale history code
  2. Inspect the entire exhaust system from the manifold to the rear sensor for leaks, cracks, and loose clamps
  3. Backprobe the rear oxygen sensor connector and watch its voltage switching rate on a scan tool while holding 2,500 rpm
  4. Check the sensor heater circuit resistance and supply voltage to rule out a lazy heater before condemning the sensor
  5. Compare upstream and downstream sensor waveforms on a lab scope to see whether the rear sensor is genuinely slow or the converter is degrading
  6. Replace the downstream oxygen sensor with the correct Chrysler-specified part if the waveform confirms slow response
  7. Clear codes and complete a full catalyst monitor drive cycle to verify the repair before returning the vehicle

Why the rear sensor looks slow but isn't

  • A small exhaust leak just ahead of the rear sensor pulls in outside oxygen and makes the sensor look lazy on the scan tool, so always smoke-test the exhaust before buying a sensor.
  • The catalyst monitor only runs under specific conditions, so a P1197 may not reset for several days after a repair, leading owners to think the fix failed when it actually worked.
  • A slow upstream sensor can make the PCM command a rich or lean swing that the rear sensor cannot follow, so check both sensors before replacing the downstream unit.
  • Chrysler has issued calibration updates for some 2.4L and 3.3L engines that change how aggressively the catalyst monitor flags a slow rear sensor, so verify the PCM is at the latest software level.
  • Replacing the catalytic converter for P1197 is a common misdiagnosis; the code points at sensor response time, and a converter fault would normally set a P0420 instead.

Can I keep driving with P1197?

The vehicle is safe to drive with P1197 because the fault only affects emissions monitoring and does not disable the engine. Avoid ignoring it for months, since a slow rear sensor can mask a developing converter or mixture problem, and get the exhaust and sensor checked before your next emissions test.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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